"A large number of writings are ascribed to him; allowing for the fact that some are probably apocryphal, his literary activity must have been tremendous. He wrote commentaries on the Posterior Analytics, and on the Physics of Aristotle. His treatise on the compotus (c. 1232) includes a discussion of the reform of the calendar, which was repeatedly quoted by subsequent writers from Bacon to Peter of Ailly. … The majority of his scientific treatises deal with physical and meteorological questions. ...He was much concerned with the complex subject called "perspective" and with optical questions in general. He was well aware of the magnifying properties of lenses, a knowledge which he probably transmitted to Bacon. (Which suggests that other items of Bacon's encyclopedic knowledge were probably obtained from Grosseteste). Many of these physical writings were ascribed by Bacon collectively to Grosseteste and to Adam Marsh. Grosseteste... showed interest in astrology and alchemy, but was remarkably free from magical fancies."